Reverse back bias, that is, increasing the reverse bias between an integrated circuit body and the sources of transistors employed in the integrated circuit, has been a tool for reducing quiescent currents such as the direct drain quiescent current IDDQ. A reverse back bias increases the threshold voltage Vt, thus reducing subthreshold currents for the integrated circuit transistors. However, reverse back bias also increases the diode leakage between the integrated circuit body and the transistors. So, there is a trade-off between reducing subthreshold current and increasing diode leakage.
The number of integrated circuit devices associated with an integrated circuit chip continues to increase while device size continues to scale downward thereby providing an increase in device density. These scaled technologies employ higher doping levels causing proportionally higher diode leakage. This increasing diode leakage thereby reduces the effectiveness of applying back bias to reduce IDDQ. In fact, for some applications, applying back bias increases IDDQ at room temperature.
Accordingly, what is needed in the art is a more effective way to compensate for these leakage effects, especially over a variety of operating temperature.